1. Field of the Invention
The invention relates to the field of microelectromechanical systems (MEMS).
Such microelectromechanical systems can be formed by etching in blocks or wafers made of semiconductor material, generally silicon.
2. Discussion of Related Art
The document FR 2 852 111 (published on 10 Sep. 2004) describes a clock-making device comprising a toothed wheel, a driving element for meshing sequentially with the toothed wheel and an actuator adapted to move the driving element according to hysteresis movement such that the driving element meshes with successive teeth of the wheel. In such a device, all the elements (toothed wheel, driving element, and actuator) are formed by microetching in the same block made of semiconductor material. The precision of the relative positioning of the elements is determined by the precision with which the block is etched.
It is preferred to connect a driving device formed by microetching in a wafer and a driven element made by means of any alternating or alternative technology (clock-making, micro-molding, machining by electroerosion or other technology).
This hybrid approach would use a standard driving device and link it to a driven element adapted to a particular application, for example an entry wheel for a reduction mechanism for a watch or clock, a cogged discoid rotor of a step-by-step rotary micromotor, or a rack of a linear engine.
This would also simultaneously create a large number of drive devices in the same block of semiconductor material (wafer).
However, when the driving device and the driven element are being connected, the relative positioning of the driving device and of the driven element is delicate. In fact, the uncertainty of positioning due for example to the manufacturing precision of the driven element and the mechanical clearances can in certain cases be greater than the amplitude of mechanical oscillations of the movement of the driving element. The result is that the driving element does not mesh with the element to be driven and the device does not function.